1. Field of the Invention
The invention relates to textile fabricating machinery, and more particularly to improvements in the construction of strand carriers for braiding machines and the like.
2. Prior Art
In the past braiding carriers have been developed for the production of fabric on braiding machines which require that strand or strands be fed to a braiding point from carriers which are actuated along a sinuous path formed in the race plate of the machine. These machines were designed primarily to braid strands of relatively flexible material such as fine yarn. Carriers used on these machines are sometimes called "Maypole"-type carriers. Typical carriers of this type are disclosed in U.S. Pat. Nos. 2,167,930, 2,236,776, and 2,459,617 which are incorporated herein by reference.
Advances in fiber technology have led to the development of new high modulus filaments or fibers. Graphite or carbon, boron and Kevlar.RTM. fibers are examples of these new fibers. Such new fibers are now incorporated into reinforced composite strands of the thermoset and thermoplastic type. These reinforced composite strands present new problems not encountered by braiding carriers disclosed above. For example when new strand materials are fabricated into a composite flat ribbon, such a ribbon is flexible only along one axis. Known carriers are wholly inadequate to handle the braiding of such stiff ribbons/strands. Specifically, the prior art devices fail to disclose mechanisms for holding and orienting the wide ribbons firmly and accurately in position long enough during the braid forming operation without twisting to ensure its firm retension by subsequently laid strands. FNT *A trademark of E. I. Dupont de Nemours and Company
Braiding equipment discussed above also operates with the carriers in a vertical plane whereby gravity is available for purposes of tensioning the strand to be braided that is wound on a bobbin. It is highly desirable to have the braider carriers capable of operating in a horizontal as well as the vertical plane wherein the weighted mechanisms for tensioning are not functional. Prior art devices also show the use of tensioning devices in the form of brakes which are held in position by lever mechanisms and/or springs. Such devices are also designed for a vertical operation and are generally too awkward and burdensome to adapt to a horizontal movement. Moreover, these types of gravity dependent, or linkage-lever mechanisms are generally unsuitable for the reinforced composite stand which is sticky, tacky, and therefore unpredictably difficult to unwind as compared to strands of flexible materials such as fine yarn for which they were designed.
The instant invention provides mechanisms which will tension a bobbin regardless of the directional orientation of the carrier itself and regardless of the tackiness of the strand on the bobbin. The instant invention accomplishes this by maintaining the orientation of the flat ribbon against a generally cylindrical pulley, not taught by the prior art and/or by providing bobbin tension through the combination of a magnetic clutch and a torsion spring.